A known truck powertrain comprises an internal combustion engine that drives road-engaging wheels through a drivetrain. A known drivetrain comprises an automatic transmission, a driveshaft, and an axle. The engine is coupled to the input of the transmission, and the driveshaft couples the output of the transmission to the axle at the ends of which the wheels are mounted.
A multi-speed axle, such as a two-speed axle, which can provide different drive ratios to the wheels, enables the driver of a vehicle to select a drive ratio that he or she deems appropriate to a particular driving situation. In the case of a vehicle having a two-speed axle, an electric selector switch for selecting a particular one of two different axle speeds (axle ratios) is accessible to the driver. That switch is part of an electric circuit that includes an actuator, such as a solenoid for example, that operates on the axle's mechanism to cause the axle to operate in either one speed range or the other.
For any of various different reasons, it may be appropriate for such an axle to be shifted from one speed range to another only under certain prevailing conditions. Hence, axle speed shifting may be allowed under some conditions and prohibited under others.
One aspect of the present invention relates to a new and unique circuit for interfacing a two-speed axle selector switch with a two-speed axle so as to allow axle speed shifting under certain conditions and to disallow axle speed shifting under others.
A presently preferred embodiment of the invention employs known circuit components connected in a new and unique cooperative association to achieve the desired objective.
The foregoing, along with further features and advantages of the invention, will be seen in the following disclosure of a presently preferred embodiment of the invention depicting the best mode contemplated at this time for carrying out the invention. The disclosure includes a drawing, briefly described as follows.